1. Field
Example embodiments relate to a method of forming conductors (e.g., metal lines and/or bumps) for semiconductor devices and conductors (e.g., metal lines and/or bumps) formed from the same. Other example embodiments relate to a method forming conductors (e.g., metal lines and/or bumps) for semiconductor packages by which an undercut problem may be solved, yield of semiconductor packages may be improved, and/or a smaller amount of inexpensive photoresist may be used to reduce manufacturing cost and conductors (e.g., metal lines and/or bumps) formed from the same.
2. Description of the Related Art
Package technology for semiconductor chips has been studied to satisfy demands for higher-speed, lighter, and/or more compact electronic products. Wafer level packages (WLPs) may have been introduced to replace conventional plastic packages. Processes for manufacturing WLPs may be performed in a wafer state and chip size packages may be realized. A general structure of a conventional WLP is shown in FIG. 1.
Referring to FIG. 1, in a WLP 10, an input and output pad 12 of a semiconductor chip 11 may be electrically connected to a solder ball 15, which is an external connection terminal, through a metal line 16 for pad redistribution formed above the semiconductor chip 11. A seed layer 14 may be formed on the semiconductor chip 11. A method of forming the metal line 16 for pad redistribution will now be described with reference to FIGS. 2A-2D.
Referring to FIG. 2A, a seed layer 22 may be formed on a semiconductor chip 21. The seed layer 22 may be formed of two metal layers, e.g., upper and lower metal layers. The upper metal layer underneath a mask 23, which will be described later, may be formed of a metal which may be plated and more easily grown. The lower metal layer on the semiconductor chip 21 may be mainly formed of a metal which may prevent or retard the upper metal layer from being diffused.
The mask 23 may be formed to have openings in which metal lines are to be formed. A surface of the seed layer 22 on which the mask 23 may have been formed may be immersed in a plating solution to be plated so as to form metal lines 24 as shown in FIG. 2B. The mask 23 may be removed as shown in FIG. 2C, and portions of the seed layer 22 on which metal lines have not been formed may be removed to form metal lines for pad redistribution as shown in FIG. 2D.
When portions of the seed layer 22a are removed, portion A shown in FIG. 2D may be etched, and thus an undercut problem may occur as shown in FIG. 3. Also, the mask 23 may be mainly photoresist and thus may not be melted in the plating solution. The mask 23 may be expensive and must be thicker than a height of metal lines. A relatively large amount of photoresist may be consumed, and thus cost may increase.
Also, an edge bead removal (EBR) may be performed along an outer circumference of a wafer to prepare a space for contacting electrodes. Yield may be decreased. Photoresist may be removed to a width of about 400 micrometers along the outer circumference of the wafer, and electrodes may contact the removed portion of the photoresist to form metal lines. Semiconductor chips positioned at an edge of the wafer may be sacrificed.